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Thick steel plate having excellent toughness and reduced softening in weld heat-affected zone

A technology of welding heat-affected and thick steel plates, which is applied in the field of thick steel plates, can solve the problems of unconsidered, HAZ toughness reduction, etc., and achieve the effects of excellent toughness, excellent mechanical properties, and HAZ softening suppression

Inactive Publication Date: 2009-12-09
KOBE STEEL LTD
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  • Description
  • Claims
  • Application Information

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Problems solved by technology

However, according to this method, even if the softening of the HAZ is suppressed, there is still a problem that the toughness of the HAZ is lowered because a coarse bainite structure is formed at the welding line portion of the HAZ.
[0015] The aforementioned methods of Patent Documents 1 to 4 are all proposed only from the viewpoint of improving HAZ toughness, and the suppression of HAZ softening is not considered at all.

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  • Thick steel plate having excellent toughness and reduced softening in weld heat-affected zone
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  • Thick steel plate having excellent toughness and reduced softening in weld heat-affected zone

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Embodiment Construction

[0029] The inventors of the present invention have conducted intensive research to provide a thick steel plate with excellent HAZ toughness and suppressed HAZ softening even when a thick steel plate with a thickness of about 60 mm or more is welded with an ultra-high heat input of more than about 60 kJ / mm. . As a result, it was found that in order to make these properties coexist, Ti, N, and B are used among the components in the steel, and it is sufficient to control the shape of the old γ grains into a flat shape as the pre-structure of the base material. In detail, it was found that: (a) Mainly, the maximum Maximize the HAZ toughness effect of fine TiN; and (b) for N, ensure hardenability by excessively adding Ti and B (in addition, Nb as needed), and by suppressing ferrite transformation, it is possible to maximize Minimizes the softening of the HAZ. Then, as a result of repeated studies in order to find the constituent requirements for effectively exerting such an effec...

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Abstract

To provide a thick steel plate having excellent HAZ toughness and suppressed HAZ softening.The thick steel plate has a composition comprising, by mass, 0.030 to 0.080% C, <=1.0% (excluding 0%) Si, 0.8 to 2.0% Mn, 0.01 to 0.10% Al, 0.015 to <0.030% Ti, >0.0055 to 0.0100% N, 0.0015 to <0.0035% B and <=0.015% (excluding 0%) Nb, and the balance Fe with inevitable impurities, and in which the flattening ratio (major axis / minor axis) of old austenite grains is >=1.5, and also satisfying inequalities (1) and (2): 2.0<=[Ti] / [N]<=4.0 (1), and 0 C22C 38 / 14 C22C 38 / 42 C22C 38 / 44 C22C 38 / 46 C22C 38 / 52 2 16 2 2006 / 11 / 23 101191176 2008 / 6 / 4 000000000 Kobe Steel Ltd. Japan Takaoka Hiroyuki Okazaki Yoshiomi wanghui min 11021 The Patent Agency of the Chinese Academy of Sciences Inside the Chinese Academy of Sciences, No.52 Sanlihe Road, Fuwai, Beijing 100864 Japan 2005 / 11 / 30 2005-347147

Description

technical field [0001] The present invention relates to a thick steel plate suitable for welded structures such as ships and marine structures, and particularly relates to a thick steel plate having excellent toughness in a heat-affected zone (HAZ) after welding and suppressed softening. Background technique [0002] In recent years, thick steel plates used in welded structures such as ships and marine structures have to be welded under stricter conditions than before as the size of welded structures increases. For example, for thick steel plates with a plate thickness of about 60mm or more, Perform ultra-large heat input welding with heat input exceeding 60kJ / mm. Under the above-mentioned heat input conditions, the welding wire (bond) part will be subjected to a thermal cycle in which the thick steel plate is heated to 1400°C and held for 50 seconds, and then cooled from 780°C to 500°C for 500 seconds. . [0003] Then, if such super heat input welding is carried out, sinc...

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C22C38/14C22C38/42C22C38/44C22C38/46C22C38/52
CPCC22C38/001C22C38/002C22C38/005C22C38/02C22C38/04C22C38/06C22C38/12C22C38/14C22C38/18
Inventor 高冈宏行冈崎喜臣
Owner KOBE STEEL LTD